U.S. patent application number 10/173965 was filed with the patent office on 2003-10-23 for thermoplastic olefin composition, process of making the composition, articles formed from the composition, and a method of forming articles therefrom.
Invention is credited to Clock, Jason B., Kakarala, Srimannarayana, Skirha, Marty D..
Application Number | 20030199637 10/173965 |
Document ID | / |
Family ID | 46280764 |
Filed Date | 2003-10-23 |
United States Patent
Application |
20030199637 |
Kind Code |
A1 |
Kakarala, Srimannarayana ;
et al. |
October 23, 2003 |
Thermoplastic olefin composition, process of making the
composition, articles formed from the composition, and a method of
forming articles therefrom
Abstract
Disclosed herein is a thermoplastic olefin composition,
comprising, based on the total weight of the composition: about 20
wt % to about 40 wt % polypropylene; about 20 wt % to about 70 wt %
ethylene copolymer; and less than or equal to about 30 wt % linear
low density polyethylene, a process of forming the thermoplastic
olefin composition, a process for vacuum forming an article
comprising the composition, an article of manufacture comprising
the composition, and an automotive assembly comprising, based on
the total weight of the assembly: about 20 to about 40 wt %
polypropylene; about 20 to about 70 wt % ethylene copolymer; and
less than or equal to about 30 wt % linear low density
polyethylene.
Inventors: |
Kakarala, Srimannarayana;
(Bloomfield Hills, MI) ; Clock, Jason B.;
(Kettering, OH) ; Skirha, Marty D.; (Vandalia,
OH) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
|
Family ID: |
46280764 |
Appl. No.: |
10/173965 |
Filed: |
June 18, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10173965 |
Jun 18, 2002 |
|
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10124939 |
Apr 17, 2002 |
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Current U.S.
Class: |
525/240 |
Current CPC
Class: |
C08L 23/16 20130101;
B29K 2105/0032 20130101; B29L 2031/302 20130101; Y02W 30/62
20150501; C08L 23/0815 20130101; B29L 2031/3014 20130101; B29C
48/022 20190201; B29C 51/08 20130101; B29K 2105/0044 20130101; B29L
2031/3008 20130101; B29K 2995/0082 20130101; B29K 2023/16 20130101;
B29C 51/04 20130101; B29C 51/002 20130101; B29K 2105/26 20130101;
B29C 48/08 20190201; B29K 2023/0625 20130101; B29B 17/0005
20130101; B29K 2023/12 20130101; C08L 23/10 20130101; C08L 23/0815
20130101; C08L 2666/06 20130101; C08L 23/10 20130101; C08L 2666/06
20130101 |
Class at
Publication: |
525/240 |
International
Class: |
C08L 023/00 |
Claims
1. A thermoplastic olefin composition, comprising, based on the
total weight of the composition: about 20 wt % to about 40 wt %
polypropylene; about 20 wt % to about 70 wt % ethylene copolymer;
and less than or equal to about 30 wt % linear low density
polyethylene.
2. The thermoplastic olefin composition of claim 1, wherein the
polypropylene concentration is about 25 wt % to about 35 wt %.
3. The thermoplastic olefin composition of claim 1, having a flex
modulus of less than about 60,000 pounds per square inch.
4. The thermoplastic olefin composition of claim 1, further
comprising less than or equal to about 15 wt % polyethylene,
polypropylene-polyethyl- ene block copolymer, random
polypropylene-polyethylene copolymer or a combination comprising at
least one of the foregoing, based on the total amount of
polypropylene present in the composition.
5. The thermoplastic olefin composition of claim 1, wherein the
polypropylene is crystalline polypropylene.
6. The thermoplastic olefin composition of claim 1, wherein the
polypropylene has a melt index of less than or equal to about 1
gram per 10 minutes, when measured according to as ASTM test method
D-1238 at 230.degree. C., employing a 2.16 kilogram mass.
7. The thermoplastic olefin composition of claim 1, wherein the
ethylene copolymer concentration is about 40 to about 65 wt %,
based on the total weight of the composition.
8. The thermoplastic olefin composition of claim 1, wherein the
ethylene copolymer includes ethylene propylene rubber, ethylene
butene rubber, ethylene octene rubber, or a combination comprising
at least one of the foregoing.
9. The thermoplastic olefin composition of claim 1, wherein the
ethylene copolymer has a glass transition temperature of less than
or equal to about negative 70.degree. C.
10. The thermoplastic olefin composition of claim 1, wherein the
ethylene copolymer includes an ethylene-propylene non-conjugated
diene copolymer (EPDM).
11. The thermoplastic olefin composition of claim 10, wherein the
non-conjugated dienes component of the EPDM includes about 6 to
about 22 carbon atoms, and has at least one readily polymerizable
carbon-carbon double bond.
12. The thermoplastic olefin composition of claim 10, wherein the
EPDM includes and uncrosslinked ethylene propylene copolymer rubber
portion having about 60 to about 80 wt % ethylene, based on the
total weight of the EPDM.
13. The thermoplastic olefin composition of claim 10, wherein the
EPDM includes a non-conjugated diene portion present at about 1 to
about 7 wt %, based on the total weight of the EPDM.
14. The thermoplastic olefin composition of claim 10, wherein the
EPDM copolymer is ethylene propylene-1,4-hexadiene, ethylene
propylene dicyclopentadiene, ethylene propylene norbomene, ethylene
propylene-methylene-2-norbornene, ethylene
propylene-1,4-hexadiene/norbom- adiene copolymer, or a combination
comprising at least one of the foregoing.
15. The thermoplastic olefin composition of claim 1, wherein the
ethylene copolymer has a melt index of less than or equal to about
1 g/10 min, when measured according to ASTM D-1238 at 230.degree.
C., employing a 2.16 kilogram mass.
16. The thermoplastic olefin composition of claim 1, wherein the
linear low density polyethylene concentration is about 5 to about
20 wt %, based on the total weight of the composition.
17. The thermoplastic olefin composition of claim 1, wherein the
linear low density polyethylene has a melt index of about 0.05 to
about 5.0 g/10 min, when measured according to method ASTM D-1238
at 230.degree. C., employing a 2.16 kilogram mass.
18. The thermoplastic olefin composition of claim 1, further
comprising a free radical initiator having a concentration of about
0.05 to about 0.5 wt % based upon the total weight of the
thermoplastic olefin composition.
19. The thermoplastic olefin composition of claim 18, wherein the
free radical initiator is an organic peroxide having a half life of
less than or equal to about 1 hour at a temperature of greater than
or equal to about 100.degree. C.
20. The thermoplastic olefin composition of claim 19, wherein the
organic peroxide is 1,1-di-t-butyl peroxy-3,3,5-trimethyl
cyclohexane, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butyl peroxy)
hexane, t-butyl-cumyl peroxide, di-t-butyl peroxide,
2,5-dimethyl-2,5-di-(t-butyl peroxy) hexyne, or a combination
comprising at least one of the foregoing.
21. The thermoplastic olefin composition of claim 1, further
comprising a pre-radical controlling co-agent component having a
concentration of about 0.05 to about 0.5 wt %, based upon the total
weight of the thermoplastic olefin composition.
22. The thermoplastic olefin composition of claim 21, wherein the
pre-radical controlling co-agent component includes
tri-methylolpropane trimethacryalate.
23. The thermoplastic olefin composition of claim 1, further
comprising a heat stabilizer, a light stabilizer, or a combination
comprising at least one of the foregoing.
24. The thermoplastic olefin composition of claim 23, wherein the
heat stabilizer includes phenolics, hydroxyl amines, phosphites, or
a combination comprising at least one of the foregoing.
25. The thermoplastic olefin composition of claim 23, wherein the
light stabilizer includes a hindered amine having a number-average
molecular weight less than about 1,000 AMU, a hindered amine having
a number-average molecular weight greater than about 1,000 AMU, or
a combination comprising at least one of the foregoing.
26. The thermoplastic olefin composition of claim 1, further
comprising a color additive having a concentration of less than or
equal to about 10 wt %, based upon the total weight of the
thermoplastic olefin composition.
27. The thermoplastic olefin composition of claim 26, wherein the
color additive is a pigment, dye, or a combination comprising at
least one of the foregoing.
28. The thermoplastic olefin composition of claim 1, wherein the
composition has a melt index of about 1 to about 20 g/10 min, when
measured according to method ASTM D-1238 at 230.degree. C.,
employing a 2.16 kilogram mass.
29. The thermoplastic olefin composition of claim 1, wherein the
melt index is less than or equal to about 10 g/10 min, when
measured according to method ASTM D-1238 at 230.degree. C.,
employing a 2.16 kilogram mass.
30. The thermoplastic olefin composition of claim 1, wherein the
melt index is less than or equal to about 6 g/10 min, when measured
according to method ASTM D-1238 at 230.degree. C., employing a 2.16
kilogram mass.
31. A process of forming a thermoplastic olefin composition
comprising: combining, based on the total weight of the
composition, about 20 wt % to about 40 wt % polypropylene; about 20
wt % to about 70 wt % ethylene copolymer; and less than or equal to
about 30 wt % linear low density polyethylene, to produce the
thermoplastic olefin composition.
32. The process of claim 31, wherein the combining includes melt
blending, in-line compounding; extruding, in-line thermoforming,
calendering or a combination comprising at least one of the
foregoing.
33. The process of claim 31, further comprising concurrent in-line
compounding and reactive extruding to form a final sheet of the
thermoplastic olefin composition.
34. The process of claim 31, further comprising precompounding.
35. The process of claim 33, wherein the sheet has a thickness of
less than or equal to about 2 mm.
36. The process of claim 33, wherein the sheet has a geometric
stipling pattern comprising half domes.
37. A thermoplastic olefin composition, comprising a reaction
product of, based on the total weight of the composition: about 20
wt % to about 40 wt % polypropylene; about 20 wt % to about 70 wt %
ethylene copolymer; less than or equal to about 30 wt % linear low
density polyethylene; and a free radical initiator, a pre-radical
controlling co-agent component, or both.
38. The thermoplastic olefin composition of claim 37, wherein the
free radical initiator has a concentration of about 0.05 to about
0.5 wt % based upon the total weight of the thermoplastic olefin
composition.
39. The thermoplastic olefin composition of claim 37, wherein the
free radical initiator is an organic peroxide having a half life of
less than or equal to about 1 hour at a temperature of greater than
or equal to about 100.degree. C.
40. The thermoplastic olefin composition of claim 39, wherein the
organic peroxide is 1,1-di-t-butyl peroxy-3,3,5-trimethyl
cyclohexane, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butyl peroxy)
hexane, t-butyl-cumyl peroxide, di-t-butyl peroxide,
2,5-dimethyl-2,5-di-(t-butyl peroxy) hexyne, or a combination
comprising at least one of the foregoing.
41. The thermoplastic olefin composition of claim 37, wherein the
pre-radical controlling co-agent component has a concentration of
about 0.05 to about 0.5 wt %, based upon the total weight of the
thermoplastic olefin composition.
42. The thermoplastic olefin composition of claim 41, wherein the
pre-radical controlling co-agent component includes
tri-methylolpropane trimethacryalate.
43. The thermoplastic olefin composition of claim 37, further
comprising a heat stabilizer, a light stabilizer, or a combination
comprising at least one of the foregoing.
44. The thermoplastic olefin composition of claim 43, wherein the
heat stabilizer includes phenolics, hydroxyl amines, phosphites, or
a combination comprising at least one of the foregoing.
45. The thermoplastic olefin composition of claim 43, wherein the
light stabilizer includes a hindered amine having a number-average
molecular weight less than about 1,000 AMU, a hindered amine having
a number-average molecular weight greater than about 1,000 AMU, or
a combination comprising at least one of the foregoing.
46. The thermoplastic olefin composition of claim 37, further
comprising a color additive having a concentration of less than or
equal to about 10 wt %, based upon the total weight of the
thermoplastic olefin composition.
47. The thermoplastic olefin composition of claim 46, wherein the
color additive is a pigment, dye, or a combination comprising at
least one of the foregoing.
48. A process for vacuum forming an article, comprising: mixing
about 20 wt % to about 40 wt % polypropylene, about 30 wt % to
about 70 wt % ethylene copolymer, and less than or equal to about
30 wt % linear low density polyethylene to form a blend, based upon
a total weight of the blend; and forming a sheet from the blend;
heating the sheet to a softening temperature; disposing the sheet
in a mold; and vacuum forming the sheet into an article.
49. The process of claim 48, wherein the vacuum forming is a female
vacuum forming process.
50. An article of manufacture comprising, based on the total
weight: about 20 wt % to about 40 wt % polypropylene; about 20 wt %
to about 70 wt % ethylene copolymer; and less than or equal to
about 30 wt % linear low density polyethylene.
51. An automotive assembly comprising, based on the total weight of
the assembly: about 20 wt % to about 40 wt % polypropylene; about
20 wt % to about 70 wt % ethylene copolymer; and less than or equal
to about 30 wt % linear low density polyethylene.
52. The automotive assembly of claim 51, wherein the assembly is a
sheathing, an instrument panel skin, a door panel, an airbag cover,
a door trim, a roof liner, a seat cover, or a combination
comprising at least one of the foregoing.
53. The automotive assembly of claim 51, further comprising less
than or equal to about 15 wt % polyethylene,
polypropylene-polyethylene block copolymer, random
polypropylene-polyethylene copolymer or a combination comprising at
least one of the foregoing, based on the total amount of
polypropylene present in the composition.
54. The automotive assembly of claim 51, wherein the polypropylene
is crystalline polypropylene.
55. The automotive assembly of claim 51, wherein the polypropylene
has a melt index of less than or equal to about 1 gram per 10
minutes, when measured according to as ASTM test method D-1238 at
230.degree. C., employing a 2.16 kilogram mass.
56. The automotive assembly of claim 51, wherein the ethylene
copolymer has a melt index of less than or equal to about 1 g/10
min, when measured according to ASTM D-1238 at 230.degree. C.,
employing a 2.16 kilogram mass.
57. The automotive assembly of claim 51, wherein the linear low
density polyethylene has a melt index of about 0.05 to about 5.0
g/10 min, when measured according to method ASTM D-1238 at
230.degree. C., employing a 2.16 kilogram mass.
58. The automotive assembly of claim 51, further comprising a free
radical initiator having a concentration of about 0.05 to about 0.5
wt % based upon the total weight of the thermoplastic olefin
composition.
59. The automotive assembly of claim 58, wherein the free radical
initiator is an organic peroxide having a half life of less than or
equal to about 1 hour at a temperature of greater than or equal to
about 100.degree. C.
60. The automotive assembly of claim 59, wherein the organic
peroxide is 1,1-di-t-butyl peroxy-3,3,5-trimethyl cyclohexane,
dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane,
t-butyl-cumyl peroxide, di-t-butyl peroxide,
2,5-dimethyl-2,5-di-(t-butyl peroxy) hexyne, or a combination
comprising at least one of the foregoing.
61. The automotive assembly of claim 51, further comprising a
pre-radical controlling co-agent component having a concentration
of about 0.05 to about 0.5 wt %, based upon the total weight of the
thermoplastic olefin composition.
62. The automotive assembly of claim 61, wherein the pre-radical
controlling co-agent component includes tri-methylolpropane
trimethacryalate.
63. The automotive assembly of claim 51, further comprising a heat
stabilizer, a light stabilizer, or a combination comprising at
least one of the foregoing.
64. The automotive assembly of claim 63, wherein the heat
stabilizer includes phenolics, hydroxyl amines, phosphites, or a
combination comprising at least one of the foregoing.
65. The automotive assembly of claim 63, wherein the light
stabilizer includes a hindered amine having a number-average
molecular weight less than about 1,000 AMU, a hindered amine having
a number-average molecular weight greater than about 1,000 AMU, or
a combination comprising at least one of the foregoing.
66. The automotive assembly of claim 51, further comprising a color
additive having a concentration of less than or equal to about 10
wt %, based upon the total weight of the thermoplastic olefin
composition.
67. The automotive assembly of claim 66, wherein the color additive
is a pigment, dye, or a combination comprising at least one of the
foregoing.
68. The automotive assembly of claim 51, wherein the composition ha
s a melt index of about 1 to about 20 g/10 min, when measured
according to method ASTM D-1238 at 230.degree. C., employing a 2.16
kilogram mass.
69. The automotive assembly of claim 51, wherein the melt index is
less than or equal to about 10 g/10 min, when measured according to
method ASTM D-1238 at 230.degree. C., employing a 2.16 kilogram
mass.
70. The automotive assembly of claim 51, wherein the melt index is
less than or equal to about 6 g/10 min, when measured according to
method ASTM D-1238 at 230.degree. C., employing a 2.16 kilogram
mass.
71. An automotive assembly, comprising a reaction product of, based
on the total weight of the composition: about 20 wt % to about 40
wt % polypropylene; about 20 wt % to about 70 wt % ethylene
copolymer; less than or equal to about 30 wt % linear low density
polyethylene; and a free radical initiator, a pre-radical
controlling co-agent component, or both.
72. A process for vacuum forming an automotive assembly,
comprising: mixing about 20 wt % to about 40 wt % polypropylene,
about 30 wt % to about 70 wt % ethylene copolymer, and less than or
equal to about 30 wt % linear low density polyethylene to form a
blend, based upon a total weight of the blend; and forming a sheet
from the blend; heating the sheet to a softening temperature;
disposing the sheet in a mold; and vacuum forming the sheet into an
article.
73. The process of claim 72, wherein the sheet has a geometric
stipling pattern comprising half domes.
74. The process of claim 72, wherein the vacuum forming is a female
vacuum forming process.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to thermoplastic olefin
compositions, specifically to a thermoplastic olefin compositions
for vacuum forming.
BACKGROUND
[0002] Vacuum forming includes both positive molds (i.e., male)
and/or negative impressions (i.e., female). A typical vacuum
forming process includes employing a negative pressure (i.e., a
vacuum), between a sheet of material to be molded and the mold
itself. The sheet is typically heated to a controlled softening
temperature and subsequently stretched to conform to the mold
contours to impart a desired shape of the part. This process may
also be assisted by a plug assist and/or one or more vacuum holes
in the mold. Once formed, the molded material is then cooled and
the excess material removed (e.g., trimmed) to yield a final part
and/or assembly.
[0003] Material properties that affect vacuum forming include melt
flow rate, depth of draw, resistance to thinning, coefficient of
friction, grain retention, and the like. However, material
properties required for negative or female vacuum forming, also
known as mold grain forming applications, are typically different
from or even in opposite to those required for male vacuum forming
applications. For example, in male vacuum forming, a high grain
retention after vacuum forming is preferred. In contrast, in female
vacuum forming, a relatively high melt flow rate to allow for
greater depth of draw and increased resistance to excessive
thinning, along with a lower coefficient of friction on tool
surfaces are preferred. Accordingly, materials suitable for male
vacuum forming may not necessarily be suitable for female vacuum
forming. Since male vacuum forming is practiced almost to the
exclusion of female vacuum forming, it would be beneficial to have
materials suitable for female vacuum forming. Of particular benefit
would be a thermoplastic olefin compositions suitable for female
vacuum forming, preferably both male and female vacuum forming.
SUMMARY
[0004] Disclosed herein is a thermoplastic olefin composition,
comprising, based on the total weight of the composition: about 20
wt % to about 40 wt % polypropylene; about 20 wt % to about 70 wt %
ethylene copolymer; and less than or equal to about 30 wt % linear
low density polyethylene.
[0005] Also disclosed herein is a process of forming a
thermoplastic olefin composition comprising: combining, based on
the total weight of the composition, about 20 wt % to about 40 wt %
polypropylene; about 20 wt % to about 70 wt % ethylene copolymer;
and less than or equal to about 30 wt % linear low density
polyethylene, to produce the thermoplastic olefin composition.
[0006] Further disclosed herein is a thermoplastic olefin
composition, comprising a reaction product of, based on the total
weight of the composition: about 20 wt % to about 40 wt %
polypropylene; about 20 wt % to about 70 wt % ethylene copolymer;
and less than or equal to about 30 wt % linear low density
polyethylene.
[0007] Additionally disclosed herein is a process for vacuum
forming an article, comprising: mixing about 20 wt % to about 40 wt
% polypropylene, about 30 wt % to about 70 wt % ethylene copolymer,
and less than or equal to about 30 wt % linear low density
polyethylene to form a blend, based upon a total weight of the
blend; and forming a sheet from the blend; heating the sheet to a
softening temperature; disposing the sheet in a mold; and vacuum
forming the sheet into an article.
[0008] Also disclosed herein is an article of manufacture
comprising, based on the total weight: about 20 wt % to about 40 wt
% polypropylene; about 20 wt % to about 70 wt % ethylene copolymer;
and less than or equal to about 30 wt % linear low density
polyethylene.
[0009] In addition, disclosed herein is an automotive assembly
comprising, based on the total weight of the assembly: about 20 wt
% to about 40 wt % polypropylene; about 20 wt % to about 70 wt %
ethylene copolymer; and less than or equal to about 30 wt % linear
low density polyethylene.
[0010] The above described and other features are exemplified by
the following detailed description.
DETAILED DESCRIPTION
[0011] Described herein are thermoplastic olefin compositions,
processes for preparing these compositions, and articles of
manufacture prepared from these compositions. Preferably, these
compositions are flexible, in that they have a flex modulus of less
than about 60,000 pounds per square inch (psi), and more preferably
less than or equal to about 50,000 psi. Also within this range, the
flex modulus is preferably greater than or equal to about 10,000
psi, and more preferably greater than or equal to about 20,000
psi.
[0012] The thermoplastic olefin composition disclosed herein
comprises about 20 to about 40 wt % polypropylene. Preferably
within this range, the polypropylene concentration is greater than
or equal to about 25 wt %. Also within this range, the
polypropylene concentration is preferably less than or equal to
about 35 wt %, with the more preferred concentration of
polypropylene being equal to about 30 wt %.
[0013] Suitable polypropylene for use herein includes, but is not
limited to, crystalline polypropylene, which may include, in
addition to the homopolymer, minor amounts of various other
materials. As used herein, minor amounts means less than or equal
to about 15 wt %, based on the total weight of the polypropylene in
the composition, and various other materials is meant to include
polyethylene, polypropylene-polyethylene block copolymer, random
polypropylene-polyethylene copolymer, and the like, as well as
combinations comprising at least one of the foregoing. In addition,
polypropylene polymers preferably include those having a melt index
of less than or equal to about 1 gram per 10 minutes (g/10 min.),
when measured according to as ASTM test method D-1238 (e.g., at
230.degree. C., employing a 2.16 kilogram (kg) mass).
[0014] The thermoplastic olefin composition further comprises about
20 to about 70 wt % ethylene copolymer. Preferably within this
range, the ethylene copolymer concentration is greater than or
equal to about 40, more preferably greater than or equal to about
50, still more preferably greater than or equal to about 55 wt %,
based on the total composition. Also within this range, the
ethylene copolymer concentration is preferably less than or equal
to about 65 wt % based on the total composition.
[0015] Suitable ethylene copolymers include, but are not limited
to, ethylene propylene rubber, ethylene butene rubber, ethylene
octene rubber, and the like, as well as combinations comprising at
least one of the foregoing. Preferably, the ethylene copolymers
have a glass transition temperature of less than or equal to about
negative 70.degree. C. (-70.degree. C.). More preferably, the
ethylene copolymer includes an ethylene-propylene non-conjugated
diene copolymer (hereinafter EPDM). The non-conjugated dienes
component of the EPDM may include about 6 to about 22 carbon atoms
and also may have at least one readily polymerizable carbon-carbon
double bond. Also preferably, the EPDM includes an uncrosslinked
ethylene propylene copolymer rubber portion having about 60 to
about 80 wt % ethylene, based on the total weight of the EPDM.
Within this range, the uncrosslinked ethylene propylene copolymer
rubber portion preferably includes greater than or equal to about
65 wt %, based on the total weight of the EPDM present. Also within
this range, the uncrosslinked ethylene propylene copolymer rubber
portion is preferably less than or equal to about 75 wt %, based on
the total weight of the EPDM present. As used herein, uncrosslinked
ethylene propylene copolymer rubber means the ethylene copolymer is
soluble in a suitable solvent (e.g., a hydrocarbon solvent).
[0016] The EPDM may also include a non-conjugated diene portion.
Preferably, the concentration of non-conjugated diene in the EPDM
is about 1 to about 7 wt % of the total weight of the EPDM present.
Preferably within this range, the concentration of non-conjugated
diene portion is greater than or equal to about 2 wt %, based on
the total weight of the EPDM present. Also preferably within this
range, the concentration of non-conjugated diene portion is less
than or equal to about 5 wt %, based on the total weight of the
EPDM present.
[0017] EPDM copolymers that are especially preferred include
ethylene propylene-1,4-hexadiene, ethylene propylene
dicyclopentadiene, ethylene propylene norbomene, ethylene
propylene-methylene-2-norbornene, and ethylene
propylene-1,4-hexadiene/norbomadiene copolymers. These materials
being preferred because they provide a depth of draw and/or a soft
touch feel to the final thermoplastic olefin composition. It is
also preferred that the ethylene copolymers have melt indices of
less than or equal to about 1 g/10 min, when measured according to
method ASTM D-1238 (e.g., at 230.degree. C., employing a 2.16
kilogram (kg) mass).
[0018] The thermoplastic olefin composition, when present, may also
comprise linear low density polyethylene (hereinafter LLDPE) in an
amount less than or equal to about 30 wt %. Preferably within this
range, the LLDPE concentration is greater than or equal to about 5
wt % based on the total composition. Also within this range, the
LLDPE concentration is preferably less than or equal to about 20,
more preferably less than or equal to about 10 wt %, based on the
total weight of the composition. Preferred LLDPE materials include
those having melt indices (test method of about 0.05 to about 5.0
g/10 min, when measured according to method ASTM D-1238 (e.g., at
230.degree. C., employing a 2.16 kilogram (kg) mass). Within this
range, the melt indices is preferably greater than or equal to
about 0.5 g/10 min. Also within this range, the melt indices is
preferably less than or equal to about 2.0, and more preferably
less than or equal to about 1.0 g/10 min.
[0019] The thermoplastic olefin composition may further comprise a
suitable polymer modifying component including, for example, a free
radical initiator, a pre-radical controlling co-agent component, a
heat stabilizer, a light stabilizer, a color additive, or a
combination comprising at least one of the foregoing.
[0020] A suitable free radical initiator is preferably an organic
peroxide, more preferably an organic peroxide having a half life of
less than or equal to about 1 hour at a temperature of greater than
or equal to about 100.degree. C. Preferred organic peroxides
include, for example, 1,1-di-t-butyl peroxy-3,3,5-trimethyl
cyclohexane, dicumyl peroxide, 2,5-dimethyl-2,5-di{t-butyl peroxy}
hexane, t-butyl-cumyl peroxide, di-t-butyl peroxide,
2,5-dimethyl-2,5-di-(t-butyl peroxy) hexyne, and the like, as well
as combinations comprising at least one of the foregoing peroxides,
with di cumyl peroxide being more preferred. Additional organic
peroxide crosslinking agents suitable for use herein also include
those listed in the Handbook of Polymer Foams and Technology,
incorporated herein by reference.sub.[MLC1]. Free radical
initiators, when present, are employed at an initial concentration
of about 0.05 to about 0.5 wt % based upon the total weight of the
thermoplastic olefin composition. Preferably, within this range,
free radical initiators are added in an amount greater than or
equal to about 0.10 wt % based upon the total weight of the
thermoplastic olefin composition. Also within this range, free
radical initiators are preferably added in an amount less than or
equal to about 0.40 wt %, based upon the total weight of the
thermoplastic olefin composition.
[0021] The thermoplastic olefin composition may also comprise a
suitable co-agent for controlling a pre-radical reaction, also
known as a pre-radical controlling co-agent component. Preferred
pre-radical controlling co-agent components include
tri-methylolpropane trimethacryalate (e.g., TM-350 commercially
available from Sartomer Co. located in Pennsylvania), and the like.
Preferably, a pre-radical controlling co-agent component, when
present, has a concentration of about 0.05 to about 0.5 wt %, based
upon the total weight of the thermoplastic olefin composition.
Preferably, within this range, the pre-radical controlling co-agent
component is added in an amount greater than or equal to about 0.10
wt % based upon the total weight of the thermoplastic olefin
composition. Also within this range, the pre-radical controlling
co-agent component is added in an amount less than or equal to
about 0.40 wt %, based upon the total weight of the thermoplastic
olefin composition.
[0022] The thermoplastic olefin composition may also include a
stabilizer such as, for example, a heat stabilizer, a light
stabilizer, and the like, as well as combinations comprising at
least one of the foregoing stabilizers. Heat stabilizers include
phenolics, hydroxyl amines, phosphites, and the like, as well as
combinations comprising at least one of the foregoing heat
stabilizers. Light stabilizers include low molecular weight
hindered amines (defined herein as having a number-average
molecular weight (AMU) less than about 1,000 AMU), high molecular
weight hindered amines (defined herein as having a number-average
molecular weight greater than about 1,000 AMU), and the like, as
well as combinations comprising at least one of the foregoing light
stabilizers. Suitable stabilizers, and the amount of stabilizer
required is readily determined according to the desired
characteristics of the finished article by one of skill in the art
without undue experimentation, with about 1 to about 4 wt %, based
on the total weight of the composition, being preferred herein.
[0023] In addition to the above modifying components, the
thermoplastic olefin compositions may also comprise a color
additive, such as a pigment, a dye, and the like, as well as
combinations comprising at least one of the foregoing color
additives. The amount of color additive is readily determined
according to the desired characteristics of the finished article by
one of skill in the art without undue experimentation. Typically
for use herein, the concentration of a color additive is less than
or equal to about 10 wt %. Preferably, the concentration of the
color additive is greater than or equal to about 0.5, more
preferably greater than or equal to about 1 wt %, based on the
total weight of the composition. Also preferred is a color additive
having a concentration of less than or equal to about 5 wt %, based
on the total weight of the thermoplastic olefin composition.
[0024] For use herein, a thermoplastic olefin composition having
properties preferred for female vacuum forming include those with a
melt index, when measured according to method ASTM D-1238 (e.g., at
230.degree. C., employing a 2.16 kilogram (kg) mass) of about 1 to
about 20 g/10 min. Preferably, within this range, the melt index is
less than or equal to about 10 g/10 min. A relatively lower
viscosity, as indicated by the composition's melt index, is also
desirable for female vacuum forming. Not wishing to be bound by
theory, it is believed this is due to the lower viscosity allowing
for a facile flow when the material is vacuum formed. Higher flow
is also desirable in order to better fill the grain being imparted
by the vacuum form tooling. A preferred melt index for male or
positive vacuum forming is less than about 6 g/10 min.
[0025] The thermoplastic olefin composition is a combination,
preferably a blend, formed using reaction extrusion compounding.
Suitable processes for forming the composition include melt
blending, preferably under high distributive mixing and low shear
conditions; in-line compounding; extruding; in-line thermoforming;
calendering; and the like, as well as combinations comprising at
least one of the foregoing processes. Furthermore, the processing
of the materials is preferably in a single manufacturing step.
Preferably the processes include concurrent in-line compounding and
reactive extruding to form a final sheet and thus eliminating steps
directed to pellet processing and the like, as well as reducing the
need for heat stabilizers and other additives. In addition,
significant time and cost savings can be realized by in-line
compounding of the composition followed by thermoforming articles
therefrom.
[0026] The production processes may be accomplished by employing
equipment including, for example, extruders, mixers, kneaders, and
the like. Suitable extruders include twin screw or single screw
extruders. A particularly well-suited extruder has a L/D (length of
screw/barrel diameter) ratio of greater than 28:1, and further
includes dispersive and distributive mixing capability. The
components may be introduced into the extruder through a combined
single feed, or through multiple feeds. In an alternate embodiment,
recycled materials (e.g., formed from scraps of a precompounded
composition) may be recycled into the process similar to or from
which it was formed, and or extruded through an extruder in a
separate process. In either embodiment, extrudate is preferably
passed from the extruder through a process suitable for forming
sheets. For example, the extrudates may be processed through a
layer die followed by embossing rollers. For female vacuum forming,
a shallow embossed pattern with a depth of less than or equal to
about 0.005 inches is desirable. A geometric stipling pattern
(e.g., geometric stiple grain) comprising half domes has been found
to be particularly preferred. This pattern is employed for the
female vacuum forming process to assist in air evacuation during
forming and for ease of coating. The extruded sheets are typically
transferred to rolls for forming articles of manufacture
therefrom.
[0027] The female vacuum forming process preferably comprises
indexing the extruded sheet into a heating station where a
pre-defined thermal pattern heats the sheet to a temperature
appropriate for vacuum forming a particular assembly. The heated
sheet is then indexed to a vacuum forming station wherein a plug
assist may push the sheet into a mold cavity. After the mold is
closed, vacuum is applied to pull the sheet into the confines of
the cavity, thus imparting a final shape of the assembly or part.
During and/or after cooling, the mold is opened (e.g., tool halves
forming the female cavity are then separated), and the formed
assembly or part, referred to in the art as the skin, is
removed.
[0028] The thickness of the sheet is preferably less than or equal
to about 2 mm thick, preferably about 1 mm thick. In addition to
being a single layer, a sheet may also comprise a plurality of
layers, at least one of which includes the thermoplastic olefin
composition disclosed herein. Thus, layers may be formed, and/or
extruded separately, and subsequently combined into a layered
sheet. In one embodiment, the first layer comprises virgin
material, and the second layer comprises a combination of virgin
material and recycled material (e.g., including previously
compounded first and second layers).
[0029] Suitable sources of polypropylene include those available
under the trade name Accpro, available from Bamberger Polymers,
Inc., Jericho, N.Y. Suitable sources of ethylene copolymer include
those available under the trade name Engage, available from Dow
Chemical, Midland, Mich. Suitable sources of LLDPE include those
available under the trade name Petrothene, available from Quantum
Chemical Inc., Australia.
[0030] The following examples illustrate specific thermoplastic
olefin compositions suitable for use herein. It should be
understood that the examples are given for the purpose of
illustration and are not intended as limitations.
1 TABLE 1 Sample # (parts per weight unit of total compound)
Component 1 2 3 4 5 6 7 8 Polypropylene 30 30 25 25 25 25 30 30
Ethylene 70 70 50 50 50 60 Copolymer LLDPE (Linear -- -- 20 25 25
25 20 10 Low Density Polyethylene) Phenolic Stabilizer (PHR) 0.2
0.2 0.2 0.2 0.2 0.2 0.2 0.2 Dicumyl -- 0.15 -- 0.2 0.3 0.15 0.15
Peroxide(PHR) Co-Agent [TM- -- 0.15 -- 0.3 0.2 0.1 0.15 0.15 350]
(PHR) Color Concentrate 4 4 4 4 4 4 4 4 (PHR)
[0031] The above compositions were tumble mixed by a ribbon blender
and fed into a twin screw extruder having a mixing screw
configuration to provide high distributive mixing at low shear, and
a residence time between about 30 to about 45 seconds. The
ingredients were compounded into pellet form. Pellets were extruded
in a single screw extruder through a slot die and calendared to a
sheet thickness of one millimeter. These sheets were vacuum formed
on a negative forming tool. The ease of vacuum forming was
determined by given a qualitative rating between 1 and 5, with 1
being the more preferred result in terms of the difficulty of start
up and the width of the process window.
[0032] Sheets were then subjected to a five finger scratch test.
This test comprises dragging a one millimeter steel tip with a 7
Newton (N) load at a set rate across the composition. The resulting
scratches were also given a qualitative rating between 1 and 5 as
above, and listed in the chart below. Material cost were also rated
between 1 and 5 as above, using commercial costs of each
ingredient. The melt strength was measured as load to break the
filaments exiting the capillary die, measured on the compounded
pellets using a capillary rheometer heated to 190.degree. C. fitted
with a Gottfert Rheotens attachment.
2 TABLE 2 Sample Number Property 1 2 3 4 5 6 7 8 Melt Strength 7 11
9 13 15 14 13 12 @ 190.degree. C. [cN] Scratch 4 3 2 1 1 1 1 2
Resistance @ 7 Newtons Ease of 5 3 4 3 1 2 2 1 Vacuum Forming
Material Cost 5 3 1 2 3 4 2 1
[0033] Referring to Table 2, the thermoplastic olefin composition
described herein exhibits scratch resistance consistent with use in
automotive interior skin applications. These thermoplastic olefin
compositions, process, and articles made therefrom, are suitable
for use in vehicle applications such as interior sheathing and so
called "Class A" surfaces, including, for example, instrument panel
skins, door panels, air bag covers, roof liners, and seat covers.
These articles can also be utilized in numerous applications,
including, but not limited to, other transportation interiors such
as those found in locomotives, airplanes, and watercrafts, home
furnishings, and luggage, among others.
[0034] The thermoplastic olefin compositions are particularly
useful in female vacuum forming. The compositions are low cost due
to the use of commodity raw materials with the concentration of
modifiers during the melt mixing process. Further cost reduction is
obtained with direct extrusion of the sheet instead of first
forming pellets. Additionally the composition comprises a high
depth of draw, e.g., greater than or equal to about 250%, enabling
the formation of complex contours and undercuts while maintaining
good grain formation.
[0035] While preferred embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. Accordingly,
it is to be understood that the apparatus and method have been
described by way of illustration only, and such illustrations and
embodiments as have been disclosed herein are not to be construed
as limiting to the claims.
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